1. Field of the Invention
The present invention relates generally to vehicle brake apparatus, and is particularly concerned with caliper disc brakes for rear drive vehicles. Still more particularly, the invention relates to disc brake adapter comprised of a composite structure.
2. Description of Related Art
Caliper disc brakes are well known in the art. Presented schematically in FIG. 1 and presented in a spatial arrangement in FIG. 2 are illustrations of a typical prior art structure of caliper disc brakes. Drive axle 10 is operatively connected to revolving disc 11 which is also connected to wheel lugs 12. As drive axle 10 rotates, wheel lugs 12 which are connected to a vehicle wheel 13 by means of a wheel hub 14 rotate wheel 13. Axle housing 15 encloses drive axle 10 which is suitably mounted therein by means of axle bearing 16.
Secured to drive axle housing 15 by way of brake adapter 17 is brake caliper 18. Brake caliper 18 functions to transmit braking forces from brake pads 23 to housing 15. Brake adapter 17 is typically bolted to drive axle housing 15 and is fitted to accept caliper 18. Caliper 18 is comprised of casting 19 accommodating at least one brake cylinder 20 in which piston 21, which is adapted for a reciprocal movement, is mounted. Cylinder 20 and piston 21 cooperate to define pressure chamber 22 which is pressurized by hydraulic fluid when the brake is actuated. Brake pad (or lining) assembly 23 is mounted on caliper 18 and is moved toward revolving disc 11 when piston 21 is moved outwardly in cylinder 20 due to brake pressure in chamber 22. In so doing, piston 21 and brake lining 23 cooperatively exert a friction force on the disc 11.
It has been general practice to use stamped sheet metal to form a brake adapter. U.S. Pat. Nos. 3,949,839 and 4,031,986 disclose such a practice.
The adapter usually carries slide pins and torque rails for the caliper. In the case of the caliper disc brakes used for rear drive vehicles, the adapter also carries a bushing for the parking (emergency) brake cable and torque rails for the parking brake. The adapter transmits all braking loads to the drive axle tube. When all of these elements are mounted on the adapter, it must possess substantially higher rigidity than an adapter made of a relatively thin sheet metal. If sheet metal is used, it must be of sufficient thickness to meet the rigidity demands of the application, and the sheet metal which would meet these demands is generally not cost effective. The required strength/rigidity can be achieved through making the adapter of nodular iron or some other material that is easily cast. However, to properly attach the cast brake adapter to the drive axle housing, several machining steps are necessary in order to conform the casting to its precise dimensions so that it can be accurately aligned and fitted to the housing. These machining operations add to the overall cost of the vehicle.